As techniques of converting image and speech information into digital data and then recording and transmitting the data, the H.264/AVC (Advanced Video Coding) standard and the like have so far been set forth. For the purpose of realizing a compression ratio exceeding this, ISO/IEC MPEG and ITU-T VCEG have established JCT-VC (Joint Collaborative Team on Video Coding) and started discussion for a next-generation method named HEVC (High Efficiency Video Coding).
As a technical candidate for the HEVC, a method called Motion Vector Competition has been proposed. The method is a proposal of a prediction vector selection method in a motion prediction mode in an encoding target macro block. In the H.264/AVC, a prediction vector has been acquired from the motion vectors owned by already-encoded macro blocks located at up, left, and upper right positions relative to the encoding target macro block by performing median arithmetic operation on the X-direction component and the Y-direction component.
On the other hand, in the motion vector competition, the motion vectors of up and left and of the nearest reference frame at the same position as the encoding target macro block are compared with each other, and then a vector closest to the motion vector of the encoding target macro block is selected as a prediction vector and transmitted as a flag.